The overall aim of this project is to localize and track the flow of information through those areas of human neocortex that respond to specific sensory inputs. To do so, we will undertake mapping and field analysis of intracranially recorded ERP (Even Related Potential) and ERD (Event Related Desynchronization) data in a population of patients with electrodes implanted for pre-surgical diagnosis of medically intractable epilepsy. Up to 128 channels of EEG will be recorded simultaneously from subdural and depth electrodes, which will enable characterization of the spatio-temporal patterns of cortical activation in a variety of perceptual and cognitive tasks. These patients routinely have high- resolution anatomical imaging via MRI and the location of the electrodes relative to individual cortical anatomy is very well-documented. We will take maximum advantages of each recording opportunity by employing state-of-the-art stimulation and response extraction techniques to minimize the number of experimental runs and trials necessary to achieve high quality ERP-ERD data, and will also employ quantitative source estimation techniques to analyze the intracranial field data that we will be acquiring. In many cases, we will also be ale to correlate our ERP/ERD results with the results of routinely performed stimulation mapping (electrical stimulation through the same electrodes). Finally, we will further constrain and verify our EEG-based mapping studies by performing the same single-trail and continuous performance experiments to map both EEG and fMRI activation in the same patients. We expect that our studies will impact both basic neuroscience and clinical applications by advancing our understanding the functional organization human neocortex and improving pre-surgical mapping of cortical function prior to surgical resections.